NOVA_USE_MOD_WSGI=True is the default in devstack since Pike,
see change If2d7e363a6541854f2e30c03171bef7a41aff745.
Therefore we can restrict the nova-wsgi-full job to just running
against stable/ocata patches.
stable/newton is intentionally left out since newton is soon to
be EOL.
Change-Id: I0d69110b466e6c82167c0ccd93b481bde6069b8f